They need to start offering discounts to existing customers. I bought the first OS X version (I think it was $20?). Then I wanted it on my iPhone, and there was no free companion app. So, another $10 for the iPhone app. Then I bought an iPad and expected to download the iOS app that I already purchased. Nope - there's another app for the iPad for another $20.
I like the app, but the developers are too greedy. It's bad enough that they charge A LOT for a simple upgraded calendar app, and charge separately for each device, but this is too much. They need to give a substantial discount to those who already spend $50 on the OS X, iPhone, and iPad apps. There's no way I'm paying $40 for an app update (and after reading the article, this is nothing more than an update).